The power congress to declare war is a?

The power of the congress to declare war is an expressed power. By definition, expressed powers are the delegated powers of a national government that are explicitly written in their respective Constitution that grants the Congress the full ability to regulate those areas. In the U.S. Constitution, Article I, Section 8, Clause 11, it is stated that the Congress is granted the power to declare war. 

The led the formation to the united states

The amendment process.